Caliper screw gauge



1.0. JACKSON.- CALIPER SCREW GAUGE. APPLICATION FILEVDSJUNEV'I, 1921.

1,43 ,3 0,] I Patented Nov. 21, 19221,

F! q 6'. I l6 4;;

Patented Nov. 21,

UNITED STATE JOSEPH DUNCAN JACKSON, 03 GLASGOW, SCOTLAND.

CALIBER SCREW GAUGE.

Application filed June 7, 1921. Serial No. 475,610.

To all whom it may concern:

Be it known that I, JOSEPH DUNCAN JAGK- soN, a subject of the King of Great Britain and Ireland, residing at 103 Barloch Street, Possilpark, Glasgow, Scotland, have invented certain new and useful Improvements in Caliper Screw Gauges; and I do hereby declare the following to be'a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and usethe same, reference being had to the accompanying drawings, and to letters or figures of reference marked thereon, which form a part of this specification.

The present invention relates to caliper screw gauges.

The constructional features which char acterize the invention will be described in the following specification and the invention defined in the annexed claims.

In the accompanying drawing which illustrates the invention F1g. 1 is a side elevatlon of a go gauge constructed in one convenient form accord in to the invention. ig. 2 is a front elevation of the same. Fig. 3 is a plan of the same. Fig. 4 shows in front elevation the anvil pieces ofa not-go gauge in their correct relative positions.

' Figs. 5 and 6 are respectively front eleva tion and plan of a modified construction of gauge. 7

Referring in the first place to Figs, 1, 2, and 3, a is the frame which may be a casting or a drop forging. The frame is formed offset as shown, the arr'nsz, a being arranged at an angle m of one hundred and twenty degrees to the U-shaped portion of the frame which connects them together. Recesses b' are accurately machined and ground in the arms. In these recesses are placed anvil pieces 0. Each anvil piece has the thread form cut in its working face (Z absolutely true to the standard form of, thread to .be gauged. The thread form is cut straight, (not curved) and is formed with a clearance angle. 10. In the present example the clearance angle is 10 degrees.

1 The working face of each anvil piece is made absolutely true with respect to the'bark face 6, that is the edges'm and n of the working face are absolutely parallel with the back face. The side faces are made absolutely true, i. e. at right angles with, the back face;

' The side faces may conveniently be ground by placlng the two anvil pieces on a mag netic table, that is a table (of a type well known) which holds the pieces in place by 0 magnetic action. This table is adapted to be moved in relation to a grinding disc or the like. The anvil pieces are placed on this table with the working facescZ in engagement with each other, and with the back faces a (and: consequently-also the faces (Z) absolutely true with respectoto the motion of the table. The table is then actuated so as to grind the side faces of the anvil pieces.

These faces are ground absolutely true with,

1. e. at right angles with, the back faces. They are ground also with the correct bevel. In this operation a jig may, with advantage, be employed.

p, p are tapered headed locking pins which hole .9 in the frame, and the head'h of the 8 screw works in a circular recess 23' cut in the frame and bears on the top of the anvil piece. r, r are the graduations on the head of thescrew. By turning either screw through a known angle, as indicated by the graduations on its head, the anvil piece which it operates may be accuratelyadjus'ted.

The anvil pieces are placed in the recesses b in the frame. The adjusting screws are screwed into the frame, andthe locking pins 77, p are-screwed up to exert a light grip on the anvil pieces. The anvil pieces are then correctly adjusted as regards their distance apart-as regards a go gaugeby engagement with a standard slip gauge equal. to the core diameter of the thread to be. measured. The locking pins are then tightened.

' In the case of a.not-go gauge, the anvil pieces are adjusted as regards their distance apart ina similarmanner and employing a suitable standard not-go slip gauge. 7

The anvil pieces of a not-go gauge are shown in Fig. 4c. The one anvil piece is provided with only a single thread form and the other with only two consecutive thread forms, as shown in the figure.

A similar screw is 80 Qt the two locking pins employed for each anvil piece one is preferably threaded ri ht hand and the other'left hand.

eferring now to Figs. 5 and 6, a modified construction of gauge is here shown. In this case the anvil pieces are held in the recesses in the frame by means of binding slips 0), which are formed with inclined. faces adapted to engage with the inclined sides of the anvil pieces as shown. These binding slips'are pulled back and are held in place by bolts ,or studs i1. In this "form of construction also, micrometenheaded adjusting screws may be employedif desired.

In either construction, a micrometerheaded adjusting screw may, if desired, be provided for one anvil piece only.

I have found that the angle a: is of great practical importance. I am of opinion tha anangle of 120 degrees is'generally a good angle, for such gauges, Bymakingfthis angle about 120 degrees, a very good light is obtained on the contact surfaces of the gauge with the screw under test; this isnot obtained when the anle is ,90'degrees.

The clearance angle 10 maybe varied from 10 degrees to suit the requirements or desiderata in particular cases.

Gauges according to the present invent-ion are applicable either ,to right or left hand screw threads.

Gauges according to the present invention allow of great speed being attained iiithe inspection of screw's'and the quick detection of faults. Their construction also tends to long life, simpl'i'cityin setting, and speed in checking the gauge. l I

The purpose of the clearance angle is twofold. I

The first purpose is this. Screw threads cut" straight (that is in straight lines-not helices) cannot engage properly with screw threads of the same contour (form andsize of thread) "cut helically (as is done on a cylindrical rod to form a screw One method of overcoming this difliculty in a caliper gauge would be .to construct the anvil pieces of very thin plate so that the acting surface is only an edge. finch acne s ruction would not however be good for practical reasons. r

Another method of overcoming the defect is that adopted according to the present inv vention. The workin face of each anvil piece is made with a clearance anele. a clearance angle is meant an angle sufiiciently great (depending on the nature or the thread) togensnre that only the protruding edge will engage with the work to be tested. This efiects the same result in gauging.

The second purpose of the clearance angle is this.

If at any time the gauge found .on test tohe inaccurate, due towear or other cause, all that is necessary is totake out the pieces, grind their front faces, (that is the faces y, 3 in Fig. l) and readjust them in the frame.

Having thus described my invention, what I claim as new and desire to secure by Lett r P ten i l. In a caliper screw gauge, the combination, with a frame having two arms, of anvil. pieces slidably carried by the said arms, one by each arm, and having working faces, to wards each other, out in thread form with a clearance angle, means for moving the said anvil pieces in the said arms to and from each other, and means for locking the said anvil pieces to the sa-idarms.

2. In a caliper screw gauge, the combination with a frame having two armsand a portion connecting together the said arms and arranged at an angle of one hundred and twenty degrees with the said arms, of

heads. for adjusting the positions of the said anvil pieces in the said arms, and means for locking the said anvil pieces to the said arms.

4. In a caliper scriew gauge, the combina tion, with a frame having two arms and a portion connectingtogether the said arms and arranged at. an angle of one hundred and twenty degrees with the said arms, of anvil pieces slidably carried by the said arms, one by each arm, and having working faces, towards each; other, out in thread form with aclearance angle, screws withgradnated heads for adjusting the positions of the said anvilpieces in the said arms,an d means for locking the said anvil pieces to the said arms.

5. In a tion, with a frame having two arms and a portion connecting together thesaid arms and arranged an angle of one hundred caliper screw gaugathe combine and, twenty degrees withathe said arms, of I anvil pieces slidably carried by the said arms, one by eacharm, and having working faces towards each other, out in thread form with a clearance angle, means for moving the said anvil pieces in the said-arms to and from each other, and tapered pins for looking the said anvil pieces to the said arms.

6. In a caliper screw gauge, the combination, with a frame having ,two arms, of anvil pieces slidably carried by the said arms, one rea h mrandlhaving wo ng fac fa ing each other, the working face of the one anvil piece being cut with only a single thread form, and the working face of the other anvil piece being cut with only two consecutive thread forms, and the working faces of both anvil pieces being cut with a clearance angle, means "for moving the said anvil pieces in the said arms to and from each other, and means for locking the said anvil pieces to the said arms.

7. In a caliper screw gauge, the combination, with a frame having two arms and a portion connecting together the said arms and arranged at an angle of one hundred and twenty degrees with the said arms, of

anvil pieces slidably carried by the said arms, one by each arm, and having working faces facing each other, the working face of the one anvil piece being cut with only a single thread form, and the working faces of both anvil piec'es being cut with a clearance angle and the working face of the other anvil piece being cut with only two consecutive thread forms, means for moving the said anvil pieces in the said arms to and from each other, and means for locking the said anvil pieces to the said arms.

I hereby sign my name to this specification.

JOSEPH DUNCAN JACKSON. 

